If we imagine a serving of French fries, a bag of chips, or a box of chicken nuggets, we probably have mixed feelings: we can’t help but start salivating thinking about how delicious they are… But we know they’re not good for our health. Nowadays, going grocery shopping or picking up lunch is an internal battle; we want something quick, tasty, and enjoyable to eat. However, we can’t pretend that we don’t know we shouldn’t eat them as often as we do.
The thing is, ultra-processed foods are like Snow White’s red apple: cheap, long-lasting, and delicious, but inherently suspicious… We know they’re too appealing to be entirely good for our health. Currently, ultra-processed foods (UPFs) account for more than 70% of the food supply in the United States. More than two-thirds of the food in the United States has undergone an industrialized process that has left it with nothing to do with the ingredients that were used.
No, is the problem with these foods the salt, sugar, and fat? Or is there something else in the industrial process that also sabotages our biology? It has reached such a point that the U.S. government itself is taking action, which is why they have assigned Dr. Kevin Hall, a leading researcher at the U.S. National Institutes of Health (NIH), to design an unprecedented experiment.
The NIH experiment
This randomized controlled study admitted 20 healthy adult participants to the NIH hospital for 28 days. They were monitored around the clock, including with specialized metabolic cameras. All participants ate an ultra-processed diet for two weeks and then a minimally processed diet for the following two weeks.
The key point is that both diets were matched for calories, sugars, fats, fiber, and sodium. In other words, the first week they were given McDonald’s chicken nuggets, and the next week they were given handmade nuggets from the hospital cafeteria. This ensured that the only significant variable was the degree of processing, as defined by the NOVA classification system.
Furthermore, the volunteers were not starved; participants were instructed to eat as much—or as little—as they wanted. This is known as ad libitum consumption.
The results were somewhat disturbing: During the week of the ultra-processed diet, participants consumed an average of 500 extra calories per day. This massive increase in energy intake meant that in just 14 days, participants gained approximately two pounds by consuming an ultra-processed diet. When they switched to the minimally processed diet, they lost all the weight.
Dr. Hall’s conclusion was clear: AUPs cause overeating and weight gain, regardless of the classic nutritional composition.
Why do we eat more ultra-processed foods?
For now, scientists have several hypotheses as to why there is an induced voracity when we eat this type of ultra-processed food. One of the main suspects is hyper-palatability. The food industry formulates ultra-processed foods with a perfect combination of ingredients. Their goal is not to nourish and meet the macro-nutritional needs of the population, but to get them to come back again and again to buy their product. To do this, they use a combination of fats, carbohydrates, and sugar that is so powerful that it overrides the normal satiety signals that the body usually sends to the brain.
Another factor to consider is caloric density: ultra-processed foods tend to have more calories per gram than natural foods. This allows us to consume a large amount of energy without the body even realizing it.
The speed of intake must also be taken into account; when it came to ultra-processed foods, participants ate them much faster. Their soft texture, which is easy to swallow and never requires cutlery to eat, helps us to gobble them down quickly and almost without chewing. This speed of intake interferes with the release of hormones that help the brain receive the “stop” signal.